Buying fruit and veg loose can save 50pc – and you can pick and choose.

Buy in bulk, save money, right? Dashing around the supermarket, my instinct is to reach for the supersize carton and the family size box, the "bigger pack, better value" label warming the cockles of my tight-fisted ticker.

But, as I stagger to the trolley and heave Brobdingnagian boxes in, I may be making unfounded assumptions. One message that came over loud and clear from your emails, when I asked for your tips and revelations about supermarket shopping, is to take your reading glasses.

You'll need them to check the "price per kilo" labels carefully, as the savings may be tiny, not big enough to justify the extra storage space, not to mention parting with your cash weeks earlier than necessary rather than leaving it to earn interest snug in your bank account. A calculator helps too, since when there's a special offer the cost per kilo may not be posted – and on "Bogofs" two small packs may well be better value than a large.

Nowhere is this more true than the produce area. Maybe that's why it's so perishing cold in there. Trolleying past the lettuces and mushrooms the other day, I was actually shivering – the frozen food aisle feels positively balmy. Is the arctic temperature by the apples and avocados to ensure all the cucumbers stay crisp and tomatoes are always in tip-top condition?

Or is it to keep us from hanging around – so we'll chuck the ready-packed bags of mushrooms and carrots in our baskets and head for the relative warmth of the dairy aisle, without noticing that, for the privilege of having the fruit and veg put into a plastic bag for us, we are paying often 50pc more and sometimes twice as much as for the loose produce.

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Actually, even I don't think that the big-boy supermarkets are really trying to freeze good sense out of us. But still, how do they get away with it? A reader, Professor John Cope of Swansea, noticed a particularly good example. His local Tesco had large displays of packs of bananas near the entrance, labelled "Buy Me £1!". Prof Cope writes: "A sample bag weighed exactly 1lb 8oz (i.e. 66p per pound). Meanwhile loose bananas had gone down to 31p per pound. No contest!" Quite.

Nor is Tesco alone. A 500g bag of parsnips in Asda costs £1 – so £2 a kilo – but loose parsnips are £1.49 a kilo. In Sainsbury's, loose courgettes cost £2 a kilo, but a bag weighing 500g is £1.75 – £3.50 a kilo. And this, even though the bags mean we can't pick and choose exactly which specimens we want?

When my local supermarket ran out of loose courgettes the other day, I saw a customer open a pack and tip it into one of the bags provided for loose veg, thus presumably saving themselves 75p. It illustrated the nonsense of this pricing policy, even if I couldn't possibly condone this sort of civil disobedience.

I asked the supermarkets why they continued this fandango. Morrisons – good for them – gave the best answer: "The price of pre-packed fruit in part reflects the costs of measuring and bagging the fruit but prices are also benchmarked against our competitors." It matches what one of the other big players said off the record: "Because it's always been like that." So, they do it because they can. And, my friends, we can refuse to play, and save ourselves pounds into the bargain. Yes we can!

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